Is there a particular type of sunscreen I should use (or not us) on my graft site?

Moh’s surgery on the face often requires surgical repair and reconstruction to reapproximate the skin edges. Flaps or direct closure techniques are used. It is important that you optimize scar healing during this phase in order to reduce longterm scars. For red scars, we use Vbeam laser, followed by fractional laser for scar topography and contour. We recommend Plato’s Scar Serum twice daily for the immediate postoperative period. Fractional laser is safe for scar laser therapy.
There are treatments for swelling and edema of the scars. If there is residual sutures or edema, we advise you to follow a scar treatment protocol that can minimize the time to recovery. Our office specializes in scar revisions for Moh’s surgery.
Best,
Dr. Karamanoukian
Realself100 Surgeon

In general, you want to use sunscreens and moisturizers on graft sites that are easy to tolerate and rarely have skin reactions.  So in general you want to use the "barrier type" sunscreens that are more similar to moisturizers and lotions.  Try and stay away from the more chemical sunscreens such as the spray ons or those that have heavy fragrances as these can be irritating to any skin or composite graft.
Ideally you'll use lotions and moisturizers with at least SPF 30 to protect your skin.  Before placement over a graft site its best to use another part of your body as a test site to make sure you don't have a reaction.  Once your graft site is well healed the likelihood of you having any reaction is low, but any inflammation on or near a graft site can be more irritating and have the potential to cause problems.  
If you have any other questions you can always reach out to the surgeon that performed the graft, another facial plastic surgeon or a dermatologist.  Good luck!